The present invention is generally related to communication devices and systems, and more particularly, to a method and apparatus accessing a plurality of communication networks.
Within the past several years, the number of radio frequency (RF) communication systems has grown from a small number of systems, each available for one type of function, to a vast number of potential systems available for providing the same type of basic services. Since the introduction of the Nordic Mobile Telephone (NMT) system, newer analogue systems have been introduced, such as Total Access Communication System (TACS), and, more recently digital systems such as the Global System for Mobile communications (GSM), DCS-1800 (Digital Cellar System), CT-2 (Cordless Telephone), and DECT (Digital European Cordless Telephone) systems. Further, there are considerable numbers of systems each serving a specific customer service demand such as the European Radio Messaging System (ERMS) for paging and Ministry of Posts and Telecommunications standard MPT 1327 (A Signalling Standard to Trunked Private Land Mobile Radio Systems) for private mobile radio applications. These systems often overlap in their coverage areas. Thereby giving users an option as to which system to select.
There is also a proliferation of new systems being developed, such as the American Digital Cellular (ADC), referred to as Interim Standard 54 (IS-54), and a Personal Digital Cellular (PDC) standard being developed in Japan, referred to as the RCR (Research and Development Centre for Radio Systems) standard 27. There is also a Code Division Multiple Access (IS-95) system being developed as a higher capacity/higher quality alternative to the existing systems. In addition to what is normally considered cellular, there are a number of Personal Communication Systems (PCS) and wireless local loop systems being developed that are all competing for customers. Some of these systems will be based on existing protocols (such as the DCS-1900 (Digital Cellular System) being based upon GSM). Also, some previous land mobile trunking systems offer dial-up telephony services. One future system currently under design is the Future Land Mobile Public Telephone System (FLMPTS).
One problem for the end user is that to be able to go anywhere in the world and use a mobile telephone, the user would need to carry a dozen or more telephones since one unit will not operate on all of the systems. In addition, even within the same system, the mobile owned by a user may have limitations built in during its original programming that prevent it from using features subsequently developed for a particular system. While there are some adaptive terminals available today that can be returned and reprogrammed (either electronically or by replacing some of the memory devices containing the programming), the user often finds themselves with an adaptive terminal that has become obsolete in just a short time.
As set forth in a patent application given serial number GB2294844 published in Great Britain on May 8, 1996, an adaptive terminal is described to enable communication by a single mobile terminal with more than one network. The mobile terminal receives from a common communications system information regarding the availability of other communication systems within the common communications system coverage area. The mobile terminal then selects one of the communications systems and receives enabling programming from the communication system. The enabling programming permits the adaptive terminal to configure itself to operate on the selected communication system.
However, such an adaptive terminal increases the memory and processor power required to be resident in the adaptive terminal, particularly if the terminal is required to compile, link and load new software in a reasonable period of time. These concerns may be particularly significant for small more simple shirt pocket sized terminals.
Accordingly, there is a need for a method and apparatus to reduce cost and complexity in a mobile unit adapted to communicate with multiple networks.